he Boston Archdiocese has formally accused attorney Roderick MacLeish Jr. of making public statements that could prevent Cardinal Bernard F. Law and other church officials from receiving fair trials in two clergy sexual abuse cases, and is preparing to ask a Superior Court judge to restrict his public comments on the lawsuits.

In a court motion served Thursday evening, the church also accused MacLeish of violating the Massachusetts Rules of Professional Conduct for lawyers, citing 31 specific statements he has made to the news media and a recent speech he delivered at Boston University Law School.

''A protective order is the only manner in which to ensure that Mr. MacLeish will not make any additional extrajudicial statements which will further erode the right of the defendants to receive fair trials,'' the church said in its motion.

But MacLeish said yesterday that his statements are well within ethical bounds, and rooted in legal documents already made public. He also noted that the church has frequently commented on the lawsuits through its archdiocesan newspaper, The Pilot, and through attorneys such as J. Owen Todd, who has publicly criticized the Superior Court judge overseeing the lawsuits, Constance M. Sweeney.

''The open comments Owen Todd has made critical of Judge Sweeney have been the subject of extensive discussion,'' MacLeish said. ''And I would never think of trying to prevent Owen from expressing his opinion because I know he has a First Amendment right to do so.''

Todd, who is Law's personal attorney, said he would not comment on the church's motion. But Joseph L. Doherty, an attorney for Bishop John B. McCormack, said, ''The purpose of the motion is to require compliance with the rules and prevent any further prejudice as we move toward trial.''

Advocates for victims of clergy sexual abuse said the church's latest legal maneuver undercuts Bishop Richard G. Lennon's repeated assertions that the archdiocese wants to settle approximately 500 sexual abuse claims quickly to avoid the trauma, risk, and expense of going to trial.

''It's just one more sign that there is little reason to hope Bishop Lennon's tenure will be any different than Law's,'' said David Clohessy, national director of the Survivors Network of those Abused by Priests.

Clohessy, citing what he described as a pattern of aggressive legal tactics used by the church, also noted an earlier church decision to require pretrial testimony from psychotherapists treating abuse victims, and a recent motion to have all the sexual abuse claims dismissed on freedom of religion grounds, under the First Amendment.

''They're trying to use the First Amendment when it's to their advantage and ignoring it when it works against them,'' he said.

The motion for an order limiting MacLeish's freedom to comment on the cases was signed by attorneys for Law, who resigned as archbishop in December, and two of his former subordinates, McCormack, now the bishop of the Manchester, N.H., diocese, and Bishop Thomas V. Daily of the Brooklyn-Queens dioceese. All three are defendants in two civil lawsuits filed by alleged victims of the Rev. Paul R. Shanley that are expected to go to trial in the spring.

More than 200 other claims by victims are subject to a 90-day legal truce -- a so-called ''stand-down'' -- that was established to allow attorneys for the church and alleged victims time to explore an out-of-court financial settlement. But MacLeish and his cocounsel, Jeffrey A. Newman, said they interpret the motion to restrict MacLeish's public comments as a sign that the church is more inclined to vigorously contest cases than to settle.

''If they want a war, they're going to get one,'' MacLeish said.

The Rev. Christopher J. Coyne, a spokesman for the archdiocese, said Lennon and the archdiocese remain committed to an out-of-court financial settlement.

The rules of conduct cited by the church in its motion prohibit lawyers from making statements ''that will have a substantial likelihood of materially prejudicing an adjudicative proceeding.''

But the rule also says lawyers are permitted to describe public legal documents, including depositions and other legal records. The rules, authorities say, are interpreted to take account of the complex balance between a defendant's right to a fair trial, an attorney's right to free expression, and the vital public interests that may be at stake in a legal proceeding.

''The rule is designed to prevent prejudice in adjudicative proceedings but it also takes into account a First Amendment protection to speak out,'' said Arnold R. Rosenfeld, the former head of the state board that oversees the conduct of lawyers.

Rosenfeld also said that Sweeney, when she considers the church motion, might determine that MacLeish's public comments were permissible if she finds that he was careful to limit his comments to publicly filed church documents.

Stephen Gillers, a legal ethics specialist at New York University School of Law who is familiar with Massachusetts rules of conduct, also said public comments that restate what has been placed in the public records are permitted, and that rules on professional conduct accommodate an attorney's right to free speech.

But Gillers also said Sweeney may find that MacLeish strayed from permissible conduct by interpreting or characterizing thousands of pages of deposition transcripts and internal church documents in a manner that may harm defendants.

Sweeney has expressed concern about some public remarks by MacLeish and the effect they may have on the ability of church officials to receive a fair trial in Greater Boston. At a court hearing last June, for example, Sweeney said, ''I just see the continuing erosion of what I see as the ability to get a fair and neutral jury pool.''

Sweeney did not mention MacLeish by name at the hearing, but the timing of her remarks made it clear she was referring to a 2 1/2-hour presentation MacLeish made to the news media last April, after the release of 800 pages of church records in the Shanley case.

''I'm making no secret of how taken aback I was by what I saw on TV,'' Sweeney said. Referring to the rules of conduct for lawyers, she added: ''This judge is going to monitor whether these rules are being complied with.''